Reenforced rubber propeller



H. T. KRAFT.

-REIENFORCED RUBBER PROPELLER. APPLICATION FILED JUNE 29, 19H.

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Ptented June 6, E922..

W/'n asses: A 20 -Pa'r:NTl oFFlcE.

HERMAN TfKRAFTLOF `AKRON', OHIO, ASSIGNOR TO THE. 'GOODYEAR TIRE & RUBBER COMPANY, OF AKRON,v OHIO', A CORPORATION OF OHIO.

REENFORCED RU'BBlElIEt PROPELLER.

Laie-,oar

Application .led' .Tune 29,

To all whom t may concern:

Be it known thatI, HERMAN T. KRAFT, a citizen of theUnited States, residing at Akron, in the lcounty of Summit and State of Ohio, provements in Reenforced-Rubber Propellers, of which the following is a specification.

Myy-present invention relates to air craft propellers, and more particularly relates to a novel propeller construction seeking to displace the usual laminated wooden type now universally employed.

The laminated wooden propeller, while having great strength and lightness, is open to a number of disadvantages in actual practice. 'Among these are the fact that. glued wooden propellers arenot proof against the action of the elements, which causes their premature deterioration. Another is that when a propeller blade is broken during the use ofthe air craft, the iying fragment is apt to encounter the gas bag, aeroplane surface, wires or other portions of the craft and do severe direct damage. It may be noted in this connection that a number of dirigible accidents are directly traceable to the fact that a broken propeller blade was thrown with such force against the gas bag as to puncture the envelope and destroy the balloon. n addition to the direct damage wreaked by a broken blade part, the unbalanced force created by rotation at high speed of the remaining propeller part tends to tear the motor from its foundations.

A still. further disadvantage of the laminated all-wood propeller resides inthe fact that it is liable to split and splinter, either when used under enemy rifle fire, or by reason of some flaw or inherent defect in the wood which the stress of usage suddenly de velops, or the almost incredible abrading action of spray when the propeller is used on a hydroplane. places'. proportionally weaken the blade, but the flying splinters are amenace to the safety of the aviator and his craft.

`Asa principal object of this invention, accordingly, it is proposed to provide a propeller blade proof against water and dampness; that it will be non-splinterable; and thatit will be` so reenforced as to prevent the throwing off of any pieces or parts of the blade.V

The above and additional obJects of a Specication of Letters Patent.

have invented new and useful Im- Not only do splintered out -reinforced rubber or constructed of a rubber so constructed that it will be 2broken pieces at a tangent; and, although somewhat heavier than a corresponding Patented June 6, 1922.

,1917.v seriai Nc. 177,721.

.there has been illustrated a preferred embodiment of the invention as it is reduced to practice, and throughout the several views of which, similar reference numbers designate corresponding parts:

Fig. l is a perspective view of a propeller blade constructed in the manner set forth in the present invention; c

Fig. 2 is a partial perspective view of the propeller blade of Fig. l;

Fig. 3 is a plan view of one of the novel types of propellers proposed herein with a modified form of interior reinforcement;

Fig. 4 is a fragmentary elevational view of a propeller blade in which the rubber is used as a veneer upon a laminated wooden reinforcement Fig. 5 is a fragmentary view of a propeller= blade having a reticulated metal reinforcement; Fig. 6 is a cross sectional view on the line 6 6 of Fig. 4;

Fig. 7 is a fragmentary elevational view of a propeller blade showing various types of metallic reinforcement which may be employed; and

Fig. 8 is anl elevational view of a framework which may desirably form the interior The material I have chosen to form the basis for the novel departure in propeller construction proposed herein is rubber, either used solidly with suitable interior reinforcements or used as a veneer upon laminated wooden propellers. A propeller built up of veneered material is proof against the action of dampness; has no tendency towards splintering when impinged upon by a small object durings its rapid revolution; can be constructed with a resistance to discharging wooden propeller, the improved propeller possesses an equal or greater strength.

. and harden Within these It is well known that rubber possesses the property of undergoing such a molecular change during vulcanization that it loses that property of resiliency which is so popularly associated with the term rubber. Some desirable rubber compound or other compounds may be utilized which will cure hard and which have, preferably, a low specific gravity.

One of the simple forms which my invention may take is illustrated in Figs. 1 and 2 in which the propeller blade as a whole is molded over a number of interiorl grouped rod or strip reinforcements l0. 'lyhese rods may be of any material which will provide the desired reinforcement for the rubber propeller blade, and may be of such dimensions as good mechanical practice dictates in the actual Working of my invention. They ma also be straight from hub to blade-tip, or may be shaped as desired to the propeller curvature'. In order to provide a firm union between the hard rubber covering and interior reinforcements, I may resort to 'the twisted, braided, or plaited wire bands l0 disclosed in Fig. 3. These bands may be so proportioned as to provide the right amount of inner reinforcement while at the same time be so constructed that the rubber may enter and penetrate the bands through the interstices of the twisted or plaited wires, in much the same manner that rubber is used to inake a union with the braided Wire beads of an automobile tire.

My present invention is, however, not limited to the types of reinforcement illustrated, as I may have resource to the employment of a laminated wooden blade 12 such as is illustrated in Figs. 4 and `6, this blade being smaller than the desired dimensions' of the finished propeller in order to permit of a substantial coating or veneer 13 of hard rubber upon the exterior of the inner blade. If a laminated wood reinforcement is employed as thus suggested, I prefer to provide a number of apertures 14 through the wooden blade in order that the rubber may flow through apertures in the manner denoted by numeral 15 of Fig. 6 to provide a union between opposite faces of the veneer or coating 13.

Again, I may have recourse to the employment of one or more strips of screen wirevlG to be used to interiorly reinforce the rubber.

blade in the manner shown in Fig. 5, the rubber being vulcanized through the interstices of the .screen in such a manner as to form a most advantageous binding together of the rubber mass.

A further modification of the underlying principle of this invention is disclosed in Fig. 7, a plurality of bars 17 being shown as located interiorly of the hard rubber mass to provide the desired strengthening elements. These bars may be of proper metal .For instance,

and of a dimension varying with the depth of the rubber in which they are embedded. I may employ heavier bars in the center of the rubber mass and may use lighter bars or wires nearer the edges of the rubber mass.

Again, without departing from the true scope of the present invention, I may employ a framework 18 of metal or a similarly appropriate material, such framework following the lines of the finished propeller shape and including, if so desired, longitudinals 19 which may be connected by cross rods or bars 2O in order to secure` a ing framework of sufficient strength.

In any case, I prefer to mold the propeller blades directly to shape and to vulcanize the molded rubber to secure that degree of hardy ness which is essential in an efficient blade.

The descriptive wording agglomerated material, set forth in the claims, should be construed to mean a material that is merely gathered together in a mold as distinguished from impregnated layers of material which are disposed in a mold with regard to the sequence of the layers.

Among the advantages of the novel type of air craft propeller herein proposed, and not already enumerated, are those of rapidity, uniformity and relative oheapness kof manufacture. The proper rubber compounds may be evolved and mixed at no greater cost than is involvedin the selection, drying, gluing, curing and the subsequent wasteful hand-turning and finishing of the laminated wooden ypropelle'rs now in practically universal use, while the process of molding my propeller blades makes for a vast saving in time of manufactureand offers a great gain in'the uniformity of the product.

Writh the use of a propeller of the type I have herein proposed, aerial navigation will be rendered much safer by protecting both the aviator and his craft from flying fragments of all too frequently broken blades. These cannot possibly be discharged by the propeller of my invention even when broken, as the internal reinforcement will obviously prevent. Moreover, my type of rubber covered and internally reinforced blade obvi- -ates the frequent necessity for repairs to split, splintered or otherwise damaged propellers.

What I claim is:

1. As a new article of manufacture, an air craft propeller including an interior reinforcing element composed of associated metal strands and a body of an agglomerated carbonaceous material molded to shape a propellerv upon the reinforcing element.

2. As a new article of manufacture, an air craft propeller constructed of an agglomerated carbonaceous material molded to shape reinforcupon interior reinforcing elements, said reinforcing elements comprising a plurality of metal elements associated to produce a uni-4 tary reinforcing element.

3. As a new articleA of manufacture, an air craft'propeller constructed of rubber molded to shape upon an interior reinforcing member, said member comprising a plurality of metal strands associated in groups.

4. As a new article of manufacture, an air craft propeller constructed of rubber molded to shape upon an interior reinforcing member, said reinforcing` element comprising a plurality of metal strands pressed to form a single cable.

5. A composite propeller blade comprising an interior reinforcing` element composed of associated metal strands and a body of carbonaceous material molded to shape a propeller upon the reinforcing element and vulcanized thereto.

6. Av propeller blade comprising a heat hardened material molded to the shape of a Iropeller blade, reinforcing elements embedded. in said material and individually comprising a plurality of intermeshed metallic elements united to form a single cable, said cables being regularly arranged Within said material and bonded therewith.

7. A body o f rubber composition molded to shape a propeller blade, metallic rein- .forcing strands arranged within said composition and each comprising a plurality of braided strands, said strands being disposed longitudinally of said blade in regular spaced relationship and vulcanized with said composition to establish bonding relation therebetween.

8. A propeller blade formed of an agglomerated moldable material embodying reinforcing metallic fibrous material embedded in the moldable material and bonded therewith in surface engagement.

9. A molded propeller blade embodying regularly arranged portions of metallic fibrous material and a heat hardened agglomerated material,

10. A propeller blade formed of an agglomerated plastic material having a plurality of regularly arranged reinforcing elements embedded therein and individually surrounded by the plastic material.

In testimony whereof, I have signed my name in the presence of two subscribing witnesses.

H. T. KRAFT. Witnesses:

JOHN E. KEATING, R. S. TRoGNER. 

